화학공학소재연구정보센터
Langmuir, Vol.33, No.32, 8052-8061, 2017
Effect of Headgroup Variation on the Self-Assembly of Cationic Surfactants with Sulfonatocalix[6]arene
The effect of headgroup variation on the association of supra molecular amphiphiles composed of 4-sulfonatocalix[6]arene (SCX6) and cationic surfactant possessing tetradecyl substituent was studied in aqueous solutions at pH 7. When the surfactant contained hydrophilic trimethylammonium, pyridinium, or 1-methylimidazolium headgroup, highly reversible temperature-responsive nanoparticle-supramolecular micelle transformation could be attained at appropriately chosen component mixing ratios and NaCl concentrations. In these cases, the substantial negative molar heat capacity change (Delta C-p) rendered nanoparticle formation strongly endothermic at low temperature, whereas the assembly to supramolecular micelle was always accompanied by enthalpy gain. The Delta C-p values became less negative when the charge density and the hydrophilic character of the surfactant headgroup diminished. The association of the more hydrophobic 6-methoxyquinolinium and quinolinium surfactants with SCX6 did not lead to supramolecular micelle formation because the self-assembly into nanoparticles was highly exothermic.